1. Technical Field
This invention relates generally to electrodeless gas discharge lamps and more particularly to the configuration and arrangement of the induction coil and the envelope in which the discharge gas is sealed.
2. Related Prior Art
Various arrangements for the induction coil and envelope of gas discharge lamps are known and generally involve locating the induction coil external of the envelope in closely adjacent relationship therewith. The envelope often has a generally cylindrical shape and is surrounded by a helically coiled induction wire. When energized, the coil excites the gas within the envelope to discharge illumination. The light which is emitted is blocked somewhat in the radial direction by the induction coil but not in the axial direction of the free end of the envelope. In many applications that employ this type of coil and envelope arrangement, the light is intended to be directed axially rather than radially and thus the blockage of light in the radial direction by the coil does not inhibit the performance of the light.
In another known arrangement, a flat spiral induction coil is supported adjacent a flat envelope and the light which evolves is emitted forwardly of the envelope, but is blocked in the opposite axial direction by the presence of the coil on the backside of the envelope. In these known applications, such blockage of the light by the coil does not present a problem since the light is intended to be directed in the forward direction only.
In other lighting applications, such as emergency flasher beacon lights of the type used, for example, on road construction pylons, barriers, signs and the like, the light is directed in opposite axial directions from a central incandescent light source through a pair of axially oppositely disposed lenses of the device. The incandescent lamp is often powered by a battery housed within a lamp base which mounts the incandescent lamp and lenses. Both the incandescent lamp and battery have a limited operating life, and as such the present emergency flasher beacons require periodic maintenance which adds cost and inconvenience to their usage.
It would be desirable to replace the incandescent lamp source with an electrodeless gas discharge lamp source since it would eliminate the presence of an electrode (i.e., a filament) which is the principal cause for the failure of incandescent lamps. An electrodeless gas discharge lamp source would further draw far less power than a comparable incandescent lamp and its usage would prolong the operating life of the battery, minimizing or altogether eliminating the requirement for frequent maintenance associated with the known incandescent beacon flashers.
There does not currently exist, however, an electrodeless gas discharge light source suitable for such a double-sided lighting application. In the case of the discharge lamps described above, the induction coil in each case would interfere with the emittance of light through at least one of the lenses and as such would impair the performance of the light.
The present invention is directed at providing such an electrodeless gas discharge lighting configuration suitable for double-sided lighting applications.